Field of the Invention
The invention relates to a method of making absorbable surgical sutures and particularly to a method of making absorbable surgical sutures based on cellulose threads and can be used in medicine and veterinary science.
At present absorbable sutures are widely used in medical practice. They do not require such a manipulation as suture removal and provide for a proper cosmeticability of the cicatrices resulting from surgical operations.
In order to be successfully used, the absorbable sutures should possess a sufficient strength. However, conventional absorbable sutures are of inadequate mechanical strength. Therefore efforts are constantly undertaken to develop novel methods of making absorbable sutures based on cellulose which are characterized by a higher mechanical strength.
Known in the art is a method of making homeostatic preparations in the form of napkins (Jackel E. C., Kenyon W. R., J. Am. Chem. Soc., vol. 64, p. 121, 1942), consisting in oxidizing cellulose with nitrogen dioxide, the oxidation process being carried out till the content of carboxyls is from 16 to 24%.
Cellulose comprising from 16 to 24% of carboxyls is of a low mechanical strength and can not be used for making surgical sutures.
There is known in the art another method of making surgical sutures (U.S. Pat. No. 2,537,979) which consists in oxidizing cellulose with nitrogen dioxide. However, as distinct from the method described above, the oxidation here is carried out till the content of carboxyls is 4 to 12.5%. The time duration of making said surgical sutures is 64 hours. The process is carried out at a temperature of 25.degree. C. Having been treated with nitrogen dioxide, the threads are washed with distilled water and dried. The ratio between the tensile strength of the sutures produced due to the treatment of the cellulose threads and the tensile strength of the cellulose threads prior to the treatment is 36.8 to 43.5%, i.e. the loss in strength is 56.5 to 63.2%. The low mechanical strength of the absorbable surgical sutures produced by the above method makes it difficult to carry out surgical manipulations.
In addition, the absorbable surgical sutures fabricated in accordance with U.S. Pat. No. 2,537,979 lost its strength, as mentioned in the Specification of the above Patent, within 5 days. The testing was carried out in a phosphate buffered solution having a pH of 7.5 at a temperature of 37.degree. C. where a suture is absorbed slower than in living tissues. No testing of the suture placed in living tissues was carried out.
Thus, the above-described method takes too much time and does not provide for the manufacture of absorbable surgical sutures having a high mechanical strength.